An electron density map at 2A resolution has been obtained of bovine Cu, Zn superoxide dismutase. Proposed work will include determination of complete atomic coordinates, using whatever additional data and refinement procedures prove suitable and necessary. A thorough description of the molecule will be published, including geometry of the metal ligands at the active site, coordinates, hydrogen bonding, differences among the 4 non-crystallographically equivalent subunits, etc. Low-resolution data are being collected for crystals of a manganese superoxide dismutase from E. coli, which is expected to have a structure unrelated to that of the Cu, Zn enzyme. The crystals of E. coli Mn enzyme are space group P21212, a equals 47A, b equals 51A, c equals 188A, with one dimer molecule of enzyme per asymmetric unit. We propose to continue toward eventual determination of a complete high-resolution structure for this molecule. We also have crystals suitable for x-ray work from the yeast mitochrondrial Mn superoxide dismutase, of space group P212121, a equal 63A, b equals 115A, c equals 125A, with one molecule (4 subunits) per asymmetric unit. We also propose to continue analyses of the topologies and folding constraints of beta sheets in the known globular protein structures.